I'm sorry, but Prust as Galchenyuk's mentor? Prust is a hard worker which makes him a leader but I don't think you want your most skilled prospect mentored by a grinder. Gally has been playing with offensive players, I'm not sure what the problem is. If anything I'd like to see him play with Plekanec. Gally, Eller, Gionta looked very promising at the end there too.
The reason that line had such good +/- is because it was sheltered, and the results were hurting the Desharnais line. That line was only broken up after it stopped performing offensively.
Gallagher right now is on fire with Pacioretty, I have no idea why you'd even consder breaking that line up.